2,2,4,4-tetrakis(difluoroamino)pentane process

ABSTRACT

2,2,4,4-Tetrakis(difluoramino)pentane and a process for its preparation. This novel composition of matter is a high energy compound for sue as a plasticizer and/or oxidizer in propellant compositions. A practical process of synthesis of this compound has been developed. This process involves the interaction of 2,4pentanedione and difluoroamine in the presence of 30 percent fuming sulfuric acid. This process is applicable to other 1,3dicarbonyl compounds, monocarbonyl compounds in general, diacetates, acetals and enol phosphates.

ieti tes atent 1 Shoults Feb. 6, 1973 9 V H V MU" TETRAKISWWLUOROAMINO}PENTANE PROCESS Inventor: Royland D. Shoults, Arab, Ala.

Assignee: The United States of America as represented by the Secretaryof the Army Filed: Nov. 12, 1968 Appl. No.: 775,999

US. Cl. ..260/583 NH, 149/109 Int. Cl ..C07c 85/04 Field of Search..260/583 NH References Cited UNITED STATES PATENTS 1/1969 Baum..260/583 3,436,419 4/1969 Rhodes ..260/583 Primary Examiner-Leland A.Sebastian Attorney-Harry M. Saragovitz, Edward J. Kelly, Herbert Berland James T. Deaton [57] ABSTRACT 2,2,4,4-Tetrakis(difluoramino)pentaneand a process for its preparation. This novel composition of matter is ahigh energy compound for sue as a plasticizer and/or oxidizer inpropellant compositionsj'A'practical 2 Claims, No Drawings BACKGROUND OFTHE INVENTION This invention relates to a novel high energy compound foruse in propellant compositions and a process of synthesis thereof. Thedesirability of high energy propellant compositions for rocket andordance projections is well-established. lf desired, a high energy metaladditive may be used in the propellant composition. However, it isfrequently desirable to achieve a high energy propellant composition byother means.

Accordingly, it is an object of this invention to provide new highenergy compounds for use in propellant compositions.

It is a particular object of this invention to provide new high energycompounds containing the functional groups, NF for use in propellants.

[t is a related object of this invention to provide such compounds whichare easily manufactured using conventional apparatus.

SUMMARY OF THE INVENTION It has been discovered that 2,2, 1,4-tetrakis(difluoroamino)pentane may be used as a novel high energycompound in propellant compositions. A practical process of synthesisthereof has been developed. This process involves the interaction of2,4- pentanedione and difluoroamine in the presence of 30 percent fumingsulfuric acid. It is carried out at ambient temperature and pressure bythe addition of the acid catalyst to the di-beta-ketone which issaturated with difluoroamine. This process is applicable to similarcompounds such as other 1,3-dicarbonyl compounds, monocarbonyl compoundsin general, diacetates, acetals and enol phosphates.

DESCRlPTlON OF THE PREFERRED EMBODIMENT These and other objects andadvantages of this invention will become more readily apparent as thefollowing detailed description proceeds.

It has been discovered that 2,2,4,4- tetrakis(difluoroamino)pentane mayadvantageously be used as a novel high energy compound in propellantcompositions. This novel compound may be prepared according to thefollowing process:

The process is carried out at ambient temperature and pressure by theaddition of the acid catalyst to 2,4-pentanedione which is saturatedwith difluoramine. This process is also applicable to otherl,3-dicarbonyl compounds, monocarbonyl compounds in general, diacetates,acetals and enol phosphates.

To fully illustrate this invention, the following example is presented.It is to be understood, however, that this example is presented merelyas a means of illustration and is not intended to limit the scope ofthis invention in any way.

Reagents 1.40.0 grams (0.4 moles) of 2,4-pentanedione.

2. 213.6 g. of 30 percent fuming sulfuric acid (0.8

moles of S0,).

3. 962 ml. of 1.98 molar difluorourea (1.9 moles).

4. 300 ml. of2 molar sulfuric acid.

Apparatus The apparatus is designed to be operated remotely and consistsof four units: l-lNF generator, reactor, washing assembly, anddistillation assembly. The apparatus is set up in such a manner as toallow general type atmospheric pressure reactions of HNF, to be carriedout.

The generator consists of a three-liter, three-neck flask equipped witha two-liter dropping funnel (constructed of polyethylene), nitrogeninlet tube (the nitrogen flow rate is controlled by means of a Mathieson622PBV flow meter), chilled water condenser, heating mantle, magneticstirrer, salt-ice trap (connected to the condenser), and a drying tower,filled with a suitable drying agent, such as the special anhydrouscalcium sulfate, highly porous granular material, Drierite (a productavailable from W. A. Hammond Drierite Co., Xenia, Ohio). The reactor,connected to the drying tower, is equipped with a thermistor probe (fortemperature indication), pressure equalized dropping funnel, magneticstirrer, Friedrichs condenser (for circulating methylene, C.), and aninlet tube for the admission of methylene chloride solvent. Anothercondenser (chilled-water) is connected to the 70C. condenser forrefluxing the solvent in the HNF elimination step. The reactor isequipped with a combination water bath for heating (heating coilconnected to a powerstat) and cooling (chilled-water inlet). A glasstube extends from the bottom of the reactor for the purpose of purgingthe reaction mixture with nitrogen. The tube is also connected to apolyethylene line for transferring the reaction product to the washingassembly.

The washing assembly consists of a one-liter flask equipped with amechanical stirrer, water aspirator vacuum line, inlets for water andaqueous sodium bicarbonate, and a drainage tube (with a three-waystopcock) leading to a l-liter separatory funnel. A fritted glassfiltering funnel is used to dry and filter the product solution. Thedistillation apparatus consists of a small three-neck flask equippedwith a magnetic stirrer, thermometer, heating mantle, 8-inchvacuumjacketed glass helices-packed column, condenser, andfraction-cutting receiver.

All of the apparatus, including the connections, is constructed ofglass, polyethylene, or the product polytetrafluoroethylene (commonlysold under the trademark Teflon).

Procedure The generator and reactor are flushed thoroughly withnitrogen, the generator is charged with 300 ml. of 2 molar sulfuricacid, the 926 ml. of difluorourea (DFU) (cold) is added to thepolyethylene dropping funnel, the 40 g. of 2,4-pentanedione is added tothe reactor, the reactor dropping funnel is charged with 213.6 g. of 30percent fuming sulfuric acid, circulation of methylene chloride (-70C.)through the Friedrichs condenser, by means of a pump, is begun and thenitrogen rate is adjusted to about 35-40 cc./min. to the generator and20-25 cc./min. to the reactor.

The acid in the generator is heated to reflux and the addition of DFU isbegun. The effluent gases (CO HNF which are produced shortly are carriedinto the reactor where the HNF condenses. On initial contact of the HNFwith the substrate there is a slight exotherm (bath temperature, 18C.,reactor temperature, 20C.) which subsides shortly. After about 200 ml.of the DFU is added, the dropwise addition of the acid catalyst is begun(exothermed to 23C.). The DFU and acid catalyst are added concurrentlyover about a 45 minute period at the end of which time the reactiontemperature is about 20C. The bath temperature is raised from about 30to 40C. and the reaction is allowed to continue for an additional 45minutes at a temperature of 2035C. The bath temperature is raised toabout 60C. and the reaction is continued for an additional 1 hour and 25minutes at 35-40C. At the end of this time about 150 ml. of solvent isadded to the reactor, the coolant flow in the -70C. condenser is turnedoff, the coolant flow to the chilled water condenser connected to thereactor is turned on, the nitrogen flow to the reactor is increased, andthe methylene chloride solvent is refluxed for ten-fifteen minutesduring which time the excess HNF is eliminated.

The reaction mixture is cooled to about 20C. and then is transferred tothe washing assembly. The reactor and transfer line are rinsed withseveral small portions of methylene chloride. After the transfer iscompleted the reaction mixture is stirred thoroughly and allowed tostand for a few minutes. The lower (acid) layer is separated anddiscarded and the methylene chloride layer is washed with water, aqueoussodium bicarbonate, and again with water. The solution is filteredthrough a frittcd glass funnel, containing anhydrous magnesium sulfate,into the distillation flask. The solvent is removed by distillation atatmospheric pressure and finally the product is distilled at reducedpressure to yield essentially pure 2,2,4,4-tetrakis(difluoramino)-pentane (25 g., 23 percent of theory).

Physical Properties Boiling Point: 47C./4.5 mm. Index of Refraction (n1.3785 Density (df'): L543 Purity (vapor phase chromatography) 99.9%

AnaL:

Calc'd. for C H N. F C, 21.75; H, 2.92; N, 20.29; F. 55.04 Found:C.21.6; 14.3.14 N, 21.3; F, 55.8 Impact sensitivity (Plcatinny): 2.8 Kg,in.,

% fire level.

The infrared spectrum exhibited strong absorption bands at 9.9 and 11microns (NF The F n.m.r. (nuclear magnetic resonance) spectrum containeda S111 let centered at -4274 cps from tr if1 uoroacetic acid Whl e theproton n.m.r. spectrum exhibited a pentuplet (CH C(NF centered at 1.75PPM (parts per million) and a singlet (CH at 2.9 PPM.

2,4-pentanedione is the first 1,3-diketone (1,3-dicarbonyl compound)that has been successfully converted to a 1,3-dicarbonyl difluoroaminoderivative. This reaction is particularly difficult to accomplish.Acidcatalyzed condensations of HNF and carbonyl compounds or theirderivatives are equilibrium controlled processes and are thus subject togreat variations in rate due to apparently slight changes in reactionconditions. Thus, acid strength, pressure, temperature and the relativeconcentrations of difluoroamine and substrate must be considered.

30 percent fuming sulfuric acid is preferred. However, other strongfuming sulfuric acid concentrations may be successfully employed, insome instances by varying the other reaction conditions such astemperature and pressure.

The general process is applicable to all 1,3-dicarbonyl compounds (orderivatives thereof). In a broader sense, it is applicable tomonocarbonyl compounds in general. It is also applicable to diacetates,acetals, and enol phosphates in general.

The product of the reaction is the fully saturated difluoroamine of theparticular starting compound.

lclaim:

1. The process of preparing2,2,4,4-tetrakis- (difluoramino) pentanecomprising:

saturating 2,4-pentanedione with at least a theoretical amount ofdifluoramine;

reacting said 2,4-pentanedione that is saturated with at least atheoretical amount of difluoramine at ambient temperature and pressurein the presence of a strong fuming sulfuric acid that is added dropwiseto said 2,4-pentanedione to catalyze the reaction to form2,2,4,4-tetrakis-(difluoramino)pentane; and recovering said 2,2,4,4-tetrakis(difluoramine) pentane.

2. The process of claim 1 wherein said process includes a concurrentaddition of said strong fuming sulfuric acid and difluoramine to said2,4-pentanedione that is saturated with at least a theoretical amount ofdifluoramine.

1. The process of preparing2,2,4,4-tetrakis-(difluoramino) pentanecomprising: saturating 2,4-pentanedione with at least a theoreticalamount of difluoramine; reacting said 2,4-pentanedione that is saturatedwith at least a theoretical amount of difluoramine at ambienttemperature and pressure in the preseNce of a strong fuming sulfuricacid that is added dropwise to said 2,4-pentanedione to catalyze thereaction to form 2,2,4,4-tetrakis-(difluoramino)pentane; and recoveringsaid 2,2,4,4-tetrakis(difluoramine) pentane.